The present embodiments relate to a robotic medical apparatus with collision detection and a corresponding method for collision detection in a robotic medical apparatus.
Medical diagnosis- and intervention systems in angiography, cardiology, neurology and hybrid ORs generally use a C-arm as the mechanical base for the imaging components, such as the X-ray source and X-ray detector. This C-arm may be positioned in a very flexible manner around a patient lying on a patient table for 2D-imaging, for example, assisted by a motorized drive. For 3D-imaging, the C-arm may be moved with semi- or fully automatic movements around the patient in order to acquire a larger number of the individual images that are necessary for the reconstruction. Alongside conventional X-ray stands, in which floor-based or ceiling-based proprietary mechanisms for the positioning of imaging components are used, robotic technology based on industrial robots has been employed for some years for the highly precise positioning and kinematics. Due to the multi-axis kinematics and the associated increase in the degrees of freedom of movement in the system, there is also an increase in system safety requirements. Specifically in a human-robot-collaboration (e.g., in scenarios, in which human and robot not only share the work space but work jointly on something (the patient), there is the risk of impeding each other, with potentially fatal consequences. In order to avoid damage, appropriate safety precautions are to be provided. Alongside the aforementioned C-arm stands, this likewise applies to the patient tables used and also to further statically mounted components of medical systems, such as ceiling mounts, display stands, “booms”, other medical arrangements, robotic assistants, or robotic medical instruments. For the aforementioned workspaces, there are no further separating safety devices such that the risk of a collision between the robot and operators is completely ruled out. Consequently, other appropriate safety measures are to be put in place to avoid a collision or a crash or to minimize harmful consequences of a collision, for example, by reducing the speed in the vicinity of a treatment couch. However, since instances of direct contact may occur in a complex environment such as an operating theatre, anywhere and at any time, there remains a residual risk of a collision. An extensive system of sensors is to be provided for this purpose.
Present-day angiography systems generally have various integrated safety mechanisms including, for example, electronic enabling switches known as Dead Man Grips (DMGs), or software-based, collision-detecting measures. An overview is provided hereafter listing safety-support sensors that have also been used hitherto as safety mechanisms.
Through the triggering of electronic switches, collisions on spring-mounted housing components of a C-arm radiation source, or on a C-arm detector with, for example, covering devices in the vicinity of the patient may be detected. Such a solution is known, for example, from U.S. Pat. No. 6,550,964 B2 “Covering device for cover elements which are mobile with relation to the other and radiology machine having such a covering device.” Electrical switch strips that may be mounted on the molding of the C-arm may act as resistive switching elements and after an appropriately severe deformation of the switch strip provide a signal that may be used to detect a collision. Suitable switch strips are known, for example, from DE 9403972 U1 “Kantenschutzprofil” [edge protection molding]. A different approach to collision detection is known from U.S. Pat. No. 5,570,770 A1 “Apparatus, in particular an x-ray examination apparatus, with arrangement for collision protection”, where in this case, the motor current is monitored by drives in order to detect a collision that has occurred. Acceleration sensors or force sensors based, for example, on strain gauges or magnetic fields are used for collision detection.
Advantageously, these sensors offer a considerable increase in safety. Nevertheless, it is only with difficulty that the sensors may be incorporated extensively, inexpensively and at the same time still in a reliable manner (e.g., on housing components with a complex design). As an example of this, electrical switch strips may be provided. Due to the geometrical shape thereof, the electrical switch strips may only be used individually and only in very limited locations. Even angles of impact greater than 45 degrees may lead to a malfunction. Collisions that occur only a few millimeters next to the strips may not be detected. In order to guarantee full coverage, a largish number of switch strips may be lined up in a row, for example, coated with foam plastic, and the surface may then be finished with an extremely flexible paint. This painted foam cover is very expensive and is not protected from destruction by sharp objects.
A further example is the aforementioned sprung-mounted housing components. These housing components are to function in every spatial position, spatial orientation and at every usual acceleration in movement. This provides that these components are only permitted to have a certain maximum weight, since the restoring force on the housing is too great to trigger in the event of a collision. The switches require an adjustment path. Since the collision with the housing component may likewise occur in this case from various directions, the adjustment path is to be guaranteed in all directions. This may only be achieved by a very complex, mechanically fragile and expensive substructure. In addition, there is the fact that separation lines and consequently edges or grooves are to be provided in order to make this adjustment path available. As a result of this, problems related to hygiene occur in the medical environment with respect to cleaning or to a necessarily expensive seal, for example.
There are also initial developments for flat collision sensors based on piezo films. This technology allows complex geometrical shapes and larger areas or surfaces to be covered. However, the relevant sensor films are to be applied and connected everywhere on the external contours where collisions may occur. This integration into the shell or outer contours is highly complex, and only selected suppliers have mastered the conversion of piezo films.